IpTahreticlounlagr-terermfereonbcjectioveitsofrethlaitsionpsrohiposatol icsotnoscuinoduesrsctaongdnititohne abnradinitsnemtwodoirfkictahtiaotncobnytrloelarhnuinmga. nOfhemaranwitahnd Mineka (2001) proposed that there is an evolved fear module in the human brain, which originates in roam- malian defence systems. Its characteristics include that it is (a) preferentially activated by, and easily conditioned to, evolutionary relevant threat stimuli;(b) it is relatively independent of cognition in the sense that it can be automatically activated and resists volition;and (c) it is controlled by subcortical and cortical systems centered on the amygdala. The fear module explains important components of anxiety disorder. The first part of the project uses individuals that are fearful of one animal (e.g., snakes) but not of another (e.g., spiders) as subjects in brain imaging experiments in which conscious access to these stimuli is manipulated by masking techniques. Further experiments with this population use magnetic resonance imaging and event-related potentials to examine brain responses to fear stimuli during visual search. Further work examines changes in brain activation as fear subsides after behavioral and pharmacological interventions targeting the central node of the fear network, the amygdala. The second part of the project is devoted to modification of the fear module as a result of Pavlovian conditioning, a kind of simple associative learning. In a systematic series of experiments human subjects will be conditioned to biologically fear- relevant stimuli (e.g., snakes) or fear-irrelevant stimuli (e.g., flowers ) by an aversive unconditioned stimulus. The basic hypothesis is that different measures of conditioning track the fear module and cognitive learning of the relationship between conditioned and unconditioned stimuli. These measures will be used in a final series of brain imaging studies the purpose of which is to unravel networks of brain structures related to conscious and nonconscious learning of the relationships between simple stimuli.